Scott Anderson writes:
This was found on the beach in Port Heiden. I’ve just never seen one on the beaches of Port Heiden I’ve heard people talk about them though and was told it’s a sea cucumber but I’m not sure. It's about the size of a dinner plate and has a rubbery texture.
College of Fisheries & Ocean Sciences (CFOS) UAF and
Ocean Integrity Research consults:
Brenda Konar, Director of the Institute of Marine Science CFOS at the University of Alaska Fairbanks (UAF), and Dr. Tom Okey with Ocean Integrity Research agree that this is a tunicate, but cannot confirm the species.
Alaska Department of Fish and Game consult:
Aaron Baldwin, writes, "That looks very much like Distaplia occidentalis, known as the Mushroom ascidian. I cannot see what the base looks like, but the color, thickness, and pattern of zooids is consistent with D. occidentalis." He notes he has seen them as large as ~15cm in diameter. Fishery Biologist, ADF&G
Erica Mitchell writes:
The mushroom ascidian Distapila occidentalis is compound tunicate, made up of many individuals that are attached. The colonies grow into globular masses, with a narrow attachment stalk. The colonies generally range from 2-10 centimeters in diameter.
Tunicates are a marine invertebrate species that generally live on the bottom (benthic level) of the ocean, attached to non-moving structures. Similar to vertebrate animals, tunicates have a skeletal rod and dorsal nerve cord (a spinal cord in humans), as well as the sensory organs necessary to detect light, and an otolith to sense gravity. They feed on plankton by filtering water through gill slits to capture food and oxygen before expelling it through an atrial siphon. They appear in a variety of colors, from a light cream or beige color to brighter pink, yellow, and orange.
There are several native and non-native tunicate species in Alaska. Non-native, or invasive, species of tunicate often travel on the hulls of ships or in the ballast water. Invasive tunicates may reproduce rapidly and out-compete native species for food and oxygen. Biologist Tammy Davis at the Alaska Department of Fish and Game has worked to identify areas around Alaska where invasive tunicates may live. To avoid letting invasive tunicates hitchhike a ride, ADF&G recommends rising gear and letting it dry completely, as well as checking and cleaning boat hulls.
For more information on tunicates, see a Tammy Davis' article Your Cousin the Sea Squirt. Alaska Fish & Wildlife News April 2010
Resources:
New Invasive Species Detected in Alaska – Didemnum Tunicate (Didemnum vexillum) is a tunicate species that is considered invasive in Alaska. **They are known to be present in Whiting Harbor near Sitka. ADF&G requests that the public avoid Whiting Harbor to prevent Didemnum Tunicate spread. By Tammy Davis, Alaska Fish & Wildlife News. February 2011
Observations From Members